<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <title>后盾人</title>
    <style>
        * {
            padding: 0;
            margin: 0;
        }

        header {
            border-bottom: solid 4px blueviolet;
            height: 30px;
            box-shadow: 0 5px 5px rgba(100, 100, 100, .6);
            margin-bottom: 30px;
            position: absolute;
            top: 0px;
            left: 0;
            right: 0;
        }

        main {
            height: 3000px;
            background: yellowgreen;
            top: 60px;
            position: absolute;
            left: 0;
            right: 0;

        }
    </style>
</head>

<body>
    <header></header>
    <main></main>

</body>

</html>